1. Field of the Invention
In ground pipe systems founded in expansive soils.
2. Prior Art
In-ground pipe systems founded in expansive soils are subject to pressures caused by the movement of the surrounding soil, due to the swelling and shrinking of the soil, which is caused by the variation of the moisture content of the surrounding soil during the changing ground water conditions. One of the characteristics of expansive type soils such as clays, is that they expand upon increase in moisture content and shrink upon decrease in moisture content. The pressure exerted upon the pipe and the pipe joint connections causes breakage of the pipe and/or disruptive effects upon the pipe joint connections, such as opening up of the joints. The pressure placed upon bends in the pipe horizontal or vertical direction, and pressures placed upon the projection flanges at the pipe joint connections, are especially critical. Once the pipe is broken or disconnected at any location, the inflow of surrounding liquid and gas into the pipe and/or the outflow of liquid or gas into the surrounding soil, is of great concern. The loss of water from a water supply system, or the infiltration of liquid into the piping system leading to a sewage treatment plant is to only name a few, cases of concern.